Does the onset of spontaneous labor at term influence fetal biophysical test parameters?

Recent data suggest that fetal breathing movement incidence declines while fetal heart rate (FHR) and body movement incidence do not change within 72 hours of spontaneous term labor. We conducted a retrospective study to determine whether the length of time from testing to spontaneous labor onset could influence these biophysical test parameters. Eighty-one normal term fetuses underwent 60-minute tests 1-40 days before the onset of spontaneous labor: 41 were tested within 7 days of labor (19 within 3 days and 22 within 4-7 days) and 40 were tested more than 7 days before labor. We simultaneously acquired and analyzed FHR baseline, frequency of accelerations between ten to 14 beats per minute and more than 15 beats per minute in amplitude, percent of time spent in breathing and moving, and fetal breath rate. These biophysical parameters were not significantly different between the groups, implying that they may continue to provide clinically useful information in the prelabor period.